Printing machine blanket cylinder cleaning device

ABSTRACT

A printing machine having a blanket cylinder which has an improved cleaning device comprising a cleaning roller with a longitudinal recess so that as the roller makes a revolution it contacts the blanket cylinder only part of the time, and can thus be brought into cleaning operation without bodily movement towards the blanket cylinder. A pawl and ratchet mechanism may be provided to cause intermittent rotation of the cleaning roller, automatically stopping at the end of a cleaning cycle.

[ July 31, 1973 United States Patent [1 1 Gates X 5 2 4 l 0 l [54] PRINTING MACHINE BLANKET CYLINDER 3,604,239 9/1971 Moxon.................

55 25X /H% 11 00M 111 ..0

Selman CLEANING DEVICE Millard 2/1898 Waite.........

- 11/1889 Cottrell......

965,117 7/1910 Muller [75] Inventor: Albert George Ronald Gates,

London, England [73] Assignee: Gestetner Limited, London, England [22] Filed:

Primary Examiner Clyde l. Coughenour Att0mey-Spencer & Kaye Feb. 3, 1971 [21] Appl. No.: 112,381

Foreign Application Priority Data [57] ABSTRACT I A printing machine having a blanket cylinder which has Feb. 7, 1970 Great 5,455/70 an improved cleaning device comprising a cleaning roller with a longitudinal recess so that as the roller makes a revolution it contacts the blanket cylinder only part of the time, and can thus be brought into cleaning operation without bodily movement towards the blan- 76. 3 50 5 2. [54.6 3 :5 0. 42 12 a ,442 B 5 3 2 a n .01 5 W im% 3 0 m2 4 u u 1 0 U "I, 1""9 a m "u "a 7 "R6 n 7 L215 C001 d St m U- -IU IF/ 1 111.10 2 00 555 [.11

ket cylinder. A pawl and ratchet mechanism may be provided to cause intermittent rotation of the cleaning [56] References Cited UNITED STATES PATENTS roller, automatically stopping at the end of a cleaning cycle.

2,612,105 9/1952 Skinner........................... 101/425 X 3,520,410 7/1970 Hutto 101/425 X 6 Claims, 7 Drawing Figures PATENIEU JUL3 1 1915 saw 1 OF 4 PATENTEDJUL'B 1 I975 SHEET 2 OF 4 tat/49,014

PATENTED JUL 3 1 I975 SHEET 3 [IF 4 PRINTING MACHINE BLANKET CYLINDER CLEANING DEVICE This invention relates to a cleaning device for the blanket cylinder of a printing machine.

It is known to clean ink from the surface of a blanket on a blanket cylinder in a printing machine by bringing into contact with the blanket cylinder a roller which has an absorbent cover soaked with solvent. Usually the roller is partially immersed in a trough containing the solvent, and is rotated in the same angular direction .as the cylinder so that the blanket is scrubbed clean by the roller surface. Theroller is brought into contact with the blanket cylinder when cleaning is desired and then moved out of contact again when the cleaning operation has been completed, the roller being moved bodily for this purpose, for example by pivoting about an axis parallel to the axis of the roller.

According to the present invention there is provided a printing machine including a blanket cylinder and a cleaning roller mounted adjacent such cylinder for rotation about a fixed axis to clean the balnket cylinder, wherein the shape of the roller is such that, as the roller makes one revolution about such axis, the surface of the roller contacts the blanket cylinder for part of the time only.

In the apparatus according to the invention, the cleaning roller will be in contact with the blanket cylinder in certain angular range of positions thereof, and be out of contact with the blanket cylinder at other angular positions or over the remainder of the angular range of positions. This means that there is no necessity to move the cleaning roller bodily in order to bring it into or out of contact with the blanket cylinder.

Means to rotate the cleaning roller may operate interm ittently to bring the appropriate part of the surface of the roller into contact with the blanket cylinder and for rotating the roller when such contact is made so that the blanket cylinder is cleaned at appropriate times.

The cleaning roller may comprise a cylinder with a recess parallel to its axis in the surface thereof. Any other form of partially recessed or incompletely cylindrical roller may be used, for instance the roller could have a D-shaped cross-section.

An advantage of the recess is that it provides a space into which a bracket or other retainer may be fixed to retain an absorbent cover fitted to the cleaning roller. The cleaning roller may be located in the position wherein it is partially immersed in a solvent bath, and a squeegee roller may be applied against it to remove excess solvent from it. The cleaning roller may have a soft rubber outer surface.

A wiper blade may usefully be attached to the cleaning roller. The blade, if provided, should be of resilient material, preferably an elastomeric material, and suitably an oil resistant elastomeric material such as I-IY- CAR.

The wiper blade ensures satisfactory final cleaning of the blanket, and is particularly useful when used in conjunction with a quick dry unit" which may be fitted to the blanket cylinder, and is a further feature of the present invention. The quick dry unit comprises an absorbent pad clamped beneath a perforated plate. This assembly is suitably fitted in the gap in the blanket cylinder. All blanket cylinders have such a gap, to accommodate fixing means for the blanket, and the quick dry unit can be fitted so that it substantially conforms to the blanket cylinder surface. When such a quick dry unit is provided in association with a wiper blade on the cleaning roller, solvent remaining on the blanket is collected by the blade and urged towards the quick dry unit, where it is absorbed by the absorbent pad. Subsequently, the solvent will evaporate through the perforated plate. Any solvent on the blanket which escapes the wiper blade will be very thinly spread, and will quickly evaporate. The wiper blade should extend to a distance from the axis of the cleaning roller at least as great as the maximum radius of that roller.

Cleaning is preferably performed during a single revolution of the cleaning roller, and therefore the rotating means may provide for rotation of the cleaning roller through one revolution to take place after, for instance, a given number of revolutions of the blanket cylinder. One possible means for rotating the cleaning roller includes two ratchet wheels mounted on a shaft to which the cleaning roller is fixed, and a pawl cooperating with each ratchet wheel, one pawl being rotatable backwards and forwards through a given are, and the other pawl being movable through a smaller arc to rotate the cleaning roller through a small angle. The ratchet wheel corresponding to the first pawl has a circumferential space without any ratchet teeth, and this space is positioned so that when the cleaning roller is out of contact with the blanket cylinder the reciprocating first pawl does not engage ratchet teeth, and does not turn the roller. When the time comes for the roller to make a cleaning revolution, the second pawl is moved to turn the roller through an angle sufficient to ensure that the first pawl is able to engage a tooth on its corresponding ratchet wheel and thus cause the roller to rotate by increments.

In order that the invention may be more clearly understood, the following description is given merely be way of example with reference to the accompanying drawings, in which:

FIG. 1, shows in diagrammatic form a blanket cylinder and one form of blanket cleaning device according to the invention;

FIG. 2, illustrates one embodiment of device according to the invention including means for rotating the cleaning roller;

FIG. 3 is a general view of one form of wash-up unit according to the invention;

FIG. 4 is a part sectional view taken on the line IV IV of FIG. 3;

FIG. 5 is a view in the direction V V of FIG. 3;

FIG. 6 is a plan view of a quick dry unit for use with the invention attachable to a blanket cylinder and comprising a further feature of the invention; and

FIG. 7 is a sectional view of the pad of FIG. 6.

In FIG. 1, a blanket cylinder 1, which is not shown completely, is adjacent a cleaning roller 2 having its axis parallel to the blanket cylinder axis and having a recess 2A parallel to its axis in its surface. The cleaning roller is partially immersed in solvent contained in a bath 3, and a small squeegeee roller 4 is provided which is sprung against the roller 2 for the purpose of removing excess solvent from its cover. The recess on the roller 2 provides a space in which a bracket or retainer may be fixed to retain the cover fitted to the roller 2, which is necessary to prevent the cover from slipping on the roller surface. In the position shown it is clear that there is no contact between the blanket cylinder and the cleaning roller, but that on rotation of the cleaning roller such contact would take place. Cleaning will normally take place with the blanket cylinder and the cleaning roller being rotated in the same angular direction so that a scrubbing action occurs.

In FIG. 2 the blanket cylinder and cleaning roller are shown in the same form, and there are also shown two ratchet wheels 5 and 6 which are locked to a spindle 7 on which the cleaning roller 2 is mounted. Two levers 8 and 9 are pivoted on the spindle 7 and each lever carries a pawl, 10 and 11 respectively, engageable with the teeth of the ratchet wheels 6 and 5 respectively. It will be seen that the ratchet wheel 6 has a circumferential space wherein no ratchet teeth are provided. In operation of the device the lever 8 reciprocates through an are as shown, and in the position of the cleaning roller wherein it does not contact the blanket cylinder, as shown, the pawl 10 on lever 8 does not engage teeth on ratchet wheel 6 and does not rotate the roller. The lever 9 may be moved in a clockwise direction to cause the ratchet wheel 5 together with the cleaning roller and the ratchet wheel 6 to rotate a certain amount. When such rotation has occured and the lever 8 reaches its extreme position in an anti-clockwise direction the pawl 10 engages a tooth on the ratchet wheel 6. Subsequently incremental rotation will follow and continue until the roller has completed one revolution. As shown the lever 9 is held by a spring 12 against an adjustable stop 13 carried by support 14. A solenoid or other actuating means, such as a cam coupled to the blanket cylinder may be used to rotate the lever 9, to cause the cylinder to be cleaned after a certain selectable number of revolutions. The speed and arc of movement of lever 8 determine the time taken for each revolution of the cleaning roller, and both factors can be varied. When pawl 10 rotates the roller clockwise, pawl 11 serves to prevent anti-clockwise movement of the roller during the periods when pawl 10 is moving anticlockwise.

FIG. 3 is a general view of one form of wash up unit according to the invention. In this view the cleaning roller is not shown, it is however adapted to be mounted between the supporting cores 15, 16, of which core 16 is urged by spring 17 into a roller supporting position. The cores are adapted to engage the inside of the cleaning roller when in position, and are supported on mounting brackets l8, 19 which hold the device in a printing machine. The left hand core is driven by a drive pin 20 on rotation of a shaft 7, to which ratchet wheels 5 and 6 are attached. In this Figure, the ratchet wheels are shown as having the same diameter, but the relative diameters of the ratchet wheels are merely a matter of choice. The sprung squeegee roller 4 is also shown in this Figure.

FIG. 4 is a part sectional view on the line IV IV of FIG. 3 but showing the blanket cylinder and cleaning roller. The blanket cylinder 1 has a blanket 41 attached to it by means of fixing means 42 in a gap 43 in the cylinder. The cleaning roller 2 has a soft cover 44 and is contacted by a squeegee roller 4 in the trough 3. As shown, the cleaning roller has a wiper 45 attached to it by a screw 46 in the recess 2A in the roller. The prefered direction of rotation of both the blanket cylinder and cleaning roller is shown, and it will be seen that the wiper blade will, as arranged, contact the blanket at the end of a cleaning cycle, i.e. one rotation of the cleaning roller, when the soft cover 44 has scrubbed the blanket.

A further optional feature of the invention is shown in FIG. 4, and also in FIGS. 6 and 7. This consists of a quick dry unit, which comprises an absorbent pad 46 located beneath a perforated plate 47. The plate 47 is curved to lie on the cylindrical surface of the blanket 41 on the blanket cylinder, and is attached by a screw to a bracket 48 in the gap 43 of the blanket cylinder, the absorbent pad 46 being held between the bracket and the perforated plate.

FIG. 5 is a detailed view of one form of ratchet and lever arranged for rotating the cleaning roller. One of the toothed wheels is behind the other and therefore not seen in the Figure. The wheel which is shown is the wheel 5 of FIG. 3, which has a full complement of teeth, while the wheel 6 of FIG. 3 has a gap where teeth are not provided. The outer wheel 5 is contacted by a pawl 51, pivoted to a lever 52, which lever is pivoted on the shaft 7 at one end and is connected to an armature 53 of a solenoid 54 at its other end. The inner wheel is contacted by a pawl 55 urged by a spring 56 and pivoted on a plate 57 also pivoted on the shaft 7. The plate is also pivotally connected to a sliding member 58 having a slot 59 engaged by a blanket cylinder shaft 60. A cam 61 on the shaft 60 contacts an abutment 62 on the sliding member 58.

It will be appreciated that the unit shown in FIGS. 3 and 4 operates in the same way as that of FIG. 1. During printing operations, the cleaning roller is maintained in an angular position wherein it does not contact the blanket cylinder, that is with the recess facing towards the blanket cylinder. When cleaning of the blanket is to take place, the cleaning roller, the lower part of which is immersed in solvent in trough 3, is rotated, in the same angular direction as the blanket cylinder, so that the blanket cylinder is scrubbed by the cleaning surface. The blanket cylinder continues to rotate, while the cleaning roller is preferably rotated through one revolution in each cleaning cycle, the cycle being completed when the wiper strip contacts the blanket, and wipes any remaining solvent into the quick dry unit from whence the solvent can gradually evaporate.

Referring again to FIG. 5, until the blanket washing operation is started, the cleaning roller remains in its rest position without touching the blanket cylinder. During printing, rotation of the blanket cylinder shaft 60 causes rotation of cam 61 and therefore rotary oscillatory movement of plate 57. Paw] 55 therefore moves to and fro, but only over the area of the corresponding ratchet wheel which does not have teeth, so that the sahft 7 and therefore the cleaning roller are not rotated. The blanket wash cycle is started by actuation of the solenoid 54, which causes rotation of lever 52 so that pawl 51 rotates its corresponding ratchet wheel a certain amount. The shaft 7 and the other ratchet wheel therefore rotate so that pawl 55 can engage a tooth, and further movement of pawl 55 continues to rotate the roller unitl one revolution is completed, when pawl 55 is again disengaged from the teeth on its associated wheel. The cycle is then complete and will not start again until solenoid 54 is again energised.

During washing, each revolution of the blanket cylinder causes rotation of the cleaning roller by an amount depending on the arc of travel of the plate 57. At the end of the cycle, the wiper blade 45 wipes any remaining fluid into the absorbent pad on the quick dry unit if this is provided.

The two ratchet wheels, one having a gap in its teeth, are provided, so that pawl 51 can prevent rotation of the cleaning roller by the blanket cylinder while pawl 55 is being drawn back over the teeth on its associated wheel.

Actuation of the solenoid is all that is required to start the cleaning cycle, and a switch in the machine controls can be connected to the solenoid to allow easy starting. Alternatively, the solenoid can be actuated automatically after a given number of revolutions of the blanket cylinder.

Many other arrangements could be constructed to cause the cleaning roller to rotate. For instance, a ratchet wheel on which two pawls act could be provided, suitably with both pawls being stationary until cleaning starts. Alternatively, pawl 11 and lever 9 may be dispensed with, and an arrangement may be provided for lengthening the stroke of pawl 10 to engage a ratchet tooth when the rotation of the roller is required. In such an arrangement means for preventing rotation of the roller by the blanket cylinder during cleaning would be required.

A reservoir for maintaining a constant level of solvent in the trough may also be provided. This may be connected to the trough by a flexible tube. Solvent level may be maintained in the trough by an arrangement wherein air can only enter the reservoir above the solvent if the level in the trough is below the correct height, thus uncovering the air inlet.

To take full advantage of the ease of operation of the cleaning roller and, in the embodiment shown, its ease of fitting, the cleaning rollers may be made as disposable items so that minimum maintainance is required.

The quick dry attachment will, if provided, greatly reduce the down time? between printing operations, that is the time devoted to cleaning the blanket cylinder. This is particularly advantageous if many short runs are made with a printing machine including a device according to the invention.

An obvious advantage of the invention is that it can not only be made to start cleaning operations automatically, but it also switches itself off.

We claim:

1. A printing machine having a blanket cylinder rotatable about a longitudinal axis, and an improved cleaning device for said blanket cylinder, said device comprising a cleaning roller having an axis of rotation and an outer surface, different parts of said outer surface being at different radial distances from said axis of rotation, the roller being mounted adjacent said cylinder with the said roller axis fixed and parallel to the said cylinder axis at a distance therefrom substantially equal to the maximum radial distance of the roller outer surface from its axis of rotation, whereby, as the roller makes one revolution about its axis the surface of the roller contacts the blanket cylinder for part of the time only, and further comprising first and second ratchet wheels, and first and second pivotal pawls respectively associated with said ratchet wheels, said ratchet wheels being rotatable with said cleaning roller, ratchet teeth disposed on a part of the circumference of said first ratchet wheel such that there is a circumferential arc wherein no ratchet teeth are provided, drive means for continuously oscillating said first pawl through an are not greater than said circumferential arc, said second pawl being intermittently oscillatable.

2. A printing machine as claimed in claim 1 wherein said drive means comprise a cam rotatable with the blanket cylinder, and an associated cam follower linked to said first pawl.

3. A printing machine as claimed in claim I further comprising a solenoid actuation of said solenoid causing oscillation of said second pawl to rotate said ratchet wheels.

4. A printing machine having a blanket cylinder rotatable about a longitudinal axis, and an improved cleaning device for said blanket cylinder, said device comprising a cleaning roller having an axis of rotation and an outer surface, different parts of said outer surface being at different radial distances from said axis of rotation, the roller being mounted adjacent said cylinder with the said roller axis fixed and parallel to the said cylinder axis at a distance therefrom substantially equal to the maximum radial distance of the roller outer surface from its axis of rotation, whereby, as the roller makes one revolution about its axis the surface of the roller contacts the blanket cylinder for part of the time only, and further comprising a wiper blade mounted longitudinally on said cleaning roller.

5. A printing machine as claimed in claim 1 and further comprising an absorbent pad on said blanket cylinder.

6. A printing machine as claimed in claim 5 and further comprising a perforated plate covering said absorbent pad on said blanket cylinder.

'l 0 It fi 4 

1. A printing machine having a blanket cylinder rotatable about a longitudinal axis, and an improved cleaning device for said blanket cylinder, said device comprising a cleaning roller having an axis of rotation and an outer surface, different parts of said outer surface being at different radial distances from said axis of rotation, the roller being mounted adjacent said cylinder with the said roller axis fixed and parallel to the said cylinder axis at a distance therefrom substantially equal to the maximum radial distance of the roller outer surface from its axis of rotation, whereby, as the roller makes one revolution about its axis the surface of the roller contacts the blanket cylinder for part of the time only, and further comprising first and second ratchet wheels, and first and second pivotal pawls respectively associated with said ratchet wheels, said ratchet wheels being rotatable with said cleaning roller, ratchet teeth disposed on a part of the circumference of said first ratchet wheel such that there is a circumferential arc wherein no ratchet teeth are provided, drive means for continuously oscillating said first pawl through an arc not greater than said circumferential arc, said second pawl being intermittently oscillatable.
 2. A printing machine as claimed in claim 1 wherein said drive means comprise a cam rotatable with the blanket cylinder, and an associated cam follower linked to said first pawl.
 3. A printing machine as claimed in claim 1 further comprising a solenoid actuation of said solenoid causing oscillation of said second pawl to rotate said ratchet wheels.
 4. A printing machine having a blanket cylinder rotatable about a longitudinal axis, and an improved cleaning device for said blanket cylinder, said device comprising a cleaning roller having an axis of rotation and an outer surface, different parts of said outer surface being at different radial distances from said axis of rotation, the roller being mounted adjacent said cylinder with the said roller axis fixed and parallel to the said cylinder axis at a distance therefrom substantially equal to the maximum radial distance of the roller outer surface from its axis of rotation, whereby, as the roller makes one revolution about its axis the surface of the roller contacts the blanket cylinder for part of the time only, and further comprising a wiper blade mounted longitudinally on said cleaning roller.
 5. A printing machine as claimed in claim 1 and further comprising an absorbent pad on said blanket cylinder.
 6. A printing machine as claimed in claim 5 and further comprising a perforated plate covering said absorbent pad on said blanket cylinder. 